On Fri, Jun 02, 2023 at 07:04:48PM -0700, Yang Shi wrote: > On Fri, Jun 2, 2023 at 4:06 PM Peter Xu <peterx@xxxxxxxxxx> wrote: > > > > When hit unstable pmd, we should retry the pmd once more because it means > > we probably raced with a thp insertion. > > > > Skipping it might be a problem as no error will be reported to the caller. > > I assume it means the user will expect prot changed (e.g. mprotect or > > userfaultfd wr-protections) applied but it's actually not. > > IIRC, mprotect() holds write mmap_lock, so it should not matter. PROT > NUMA holds read mmap_lock, but returning 0 also doesn't matter (of > course retry is fine too). just skip that 2M area. True. > The userfaultfd-wp is your call :-) Yeah I think uffd should still be a problem. I'll reword the commit message (by dropping mprotect example) in the new version. If you have time feel free to have a look at patch 4, where I think it's a bug for pagemap too (I didn't check as close as all the rest; the memcg one might be suspecious, that's also in patch 4). Thanks! -- Peter Xu
